1. The Field of the Invention
Implementations of the present invention relate in part to air conditioning systems, such as used in automobiles.
2. Background and Relevant Art
For the past several decades, air conditioning systems have been used in automobiles and other motor vehicles during hot weather to provide more comfortable conditions for drivers and other vehicle occupants. Typically, an air conditioning system uses a refrigerant, which it compresses and expands at various points to cool warm air.
In general, vehicular air conditioning systems use energy from an active power source, such as an operating vehicle engine, to compress air conditioner refrigerant. One conventional air conditioner system, for example, might be configured with an air conditioner refrigerant compressor (“compressor”) that is selectively coupled to a vehicle engine. In particular, the compressor might be selectively coupled to an engine fan belt, via a magnetic clutch and engine fan pulley system. When an operator engages the air conditioner, therefore, the air conditioning system engages the magnetic clutch, which then couples the air conditioner compressor to the engine (i.e., through the engine fan and engine fan pulley), and translates engine power to the compressor. The compressor of the air conditioning system can then use this engine power to compress the refrigerant.
Once compressed, conventional air conditioning systems pass the refrigerant ultimately to an expansion valve (or orifice tube) in an air box heat exchanger/evaporator (“heat exchanger”) where the refrigerant may pass through a counter-current heat exchange with incoming air. Conventional air conditioning systems then pass the at least semi-condensed/compressed refrigerant from the heat exchanger back to the compressor for re-compression. Accordingly, the compressed refrigerant passes into the air box heat exchanger from the “high pressure side” of the air conditioning system, while the expanded refrigerant exits the heat exchanger into what is termed the “low pressure side” of the air conditioning system.
In general, and without use of the compressor, the exchange of differentially pressurized refrigerant volumes between the higher and lower pressure sides of the air conditioning system through the expansion valve will tend to equalize the overall refrigerant pressurization in the air conditioning system. That is, the pressure of refrigerant in the lower pressure side of the air conditioning system tends to increase with increased refrigerant volume, as well as with the addition of heat. Simultaneously, the pressure on the high pressure side of the air conditioning system tends to decrease as pressurized refrigerant passes into the heat exchanger. Ultimately, therefore, the air conditioning system will need to re-pressurize the refrigerant for it to be useful for cooling purposes.
Determining when to re-pressurize (i.e., “compress”) the refrigerant is typically done any number of ways. In one conventional example, an air conditioning system might use a high/low pressure switch to monitor the refrigerant pressurization on the high and/or low pressure sides. For example, if the air conditioning system detects that refrigerant pressurization on the low pressure side is above a desired threshold, the air conditioning system might thus deduce that pressure on the high pressure side of the air conditioning system is too low, and thus engage the magnetic clutch (i.e., and engage the compressor). The air conditioning system can then compress the lower-pressure refrigerant in the low pressure side, and pass the newly-compressed refrigerant to the high pressure side. Once the pressurization on the low and/or high side of the air conditioning system hits a particular threshold, the air conditioning system might then disengage the magnetic clutch, and stop the compressor.
Although the air conditioning system might only engage the compressor at select pressure thresholds, each engagement nevertheless applies a particular load on the active power source (i.e., the engine). Although this added load on the engine may appear to be comparatively low, each added load on the power source/engine results in a need to consume additional fuel. In some situations, for example, operation of the compressor can reduce overall vehicle fuel efficiency (e.g., mpg/kpl) by as much as 25 percent or more. This simply means that a vehicle will typically consume more fuel during warmer periods (e.g., when using the air conditioner), which of course adds financial costs of additional fuel purchases. This also means that operating an air conditioner can ultimately result in additional fossil fuel exhaust expelled into the environment.
Manufacturers of hybrid vehicles (i.e., engine and battery-powered hybrids) attempt to circumvent some of these engine load/fuel efficiency problems with vehicles that use large-capacity batteries together with regenerative brakes. Such hybrid vehicles couple charging of the large-capacity battery at least in part to waste kinetic energy generated only during braking actions (using dynamic brakes, which charge the battery). The additional costs associated with the larger battery, the complex mechanisms used by the hybrid vehicle to capture waste energy, and the extra weight added thereby, however, tend to make conventional hybrid vehicles fairly expensive. These complex mechanisms also tend to be expensive to maintain over time, and such costs could tend to offset some of the savings associated with the added fuel economy.